Anion activation

Addition polymerization through anionic active species. This is discussed in the next section. 

Dietrich, Lehn and Sauvage recognized not only the possibility of enclosing a cation completely in a lipophilic shell, but they also recognized the potential for using such systems for activating associated anions. This is made particularly clear in a paper which appeared some years later One of the original motivations for our work on cryptates rested on their potential use for salt solubilization, anion activation and phase transfer catalysis . This particular application is discussed below in Sect. 8.3. 

Aqueous solutions of dyes ean also be employed instead of water. In the ease of hydrophilic dyes such as methylene blue or patent fast blue the transparent background of the TLC/HPTLC plate is stained blue. Pale spots occur where there are nonwetted zones. Dauble [89] detected anion-active detergents in this way on silica gel layers as pale zones on a blue background with palatine fast blue GGN... 

Eosin Flavonoids Morin Flavonol, fisetin, robinetin Quercetin Rutin condensation products of urea, formaldehyde and methanol [126], pesticide derivatives [127] sweetening agents [128, 129] anion-active and nonionogenic surface-active agents [130] steroids, pesticides [29,132, 133] pesticides [134—137] vanadium in various oxidation states [138] uracil derivatives [139]... 

Not only cationic, but also anionic, species can be retained without addition of specially designed ligands. The anionic active [FFPt(SnCl3)4] complex has been isolated from the [NEt4][SnCl3] solvent after hydrogenation of ethylene [27]. The PtCl2 precursor used in this reaction is stabilized by the ionic salt (liquid at the reaction temperature) since no metal deposition occurs at 160 °C and 100 bar. The catalytic solution can be used repeatedly without apparent loss of catalytic activity. 

It seems reasonable to assume that both polarity and polarization potential of the anions must be taken into account in the definition of anion activity. It is quite indicative to arrange the anions by increasing order of the product of the polarity and polarization potential, a-Z/r,... 

Sodium dodecyl sulfate is the universal analytical standard for the determination of anionic and cationic active matter. It is used to determine the analytical concentration factor of the cationic surfactant in the titration of anionic active matter and as titrant to determine the cationic active matter. 

An analysis of alcohol and alcohol ether sulfates should determine the anionic active matter, the unsulfated matter, the inorganic sulfate content, the chloride content, and water. Other more precise analysis must determine the alkyl chain distribution of the alcohol and in the case of alcohol ether sulfates the number of ethoxy groups and its distribution, as well as other more specialized determinations, such as the content of 1,4-dioxane and other impurities. 

ISO 2271 1989, Surface active agents Determination of anionic-active matter by manual or mechanical direct two-phase titration procedure. 

Dissolve a sample containing 0.5 meq anion-active material with a ether carboxylic acid group in alcohol and neutralize with 0.5 N NaOH on phenol-phthalein. Transfer this solution to a 250-ml graduated flask with a stopper and make up to the mark with distilled water. Introduce into a 100-ml graduated cylinder with a stopper ... 

The types of analyses discussed in this section can be divided into two groups active matter and impurities. Several methods assess the anionic surfactant (active matter) content of the AOS product. These are particularly important since detergent performance is directly related to surfactant concentration. The different types of anionic active material are identified and quantified. 

As mentioned, AOS is a complex mixture of anionic active substances the nature of which is dependent on the quality of the olefin feed and the manufacturing processes employed. Formulations utilizing AOS are developed according to the level and type of these active species. Analytical procedures are therefore required to define their level and nature. 

It is sometimes said that this electrode is reversible with respect to the anion. This claim must be examined in more detail. An electrode potential that depends on anion activity still constitutes no evidence that the anions are direct reactants. Two reaction mechanisms are possible at this electrode, a direct transfer of chloride ions across the interface in accordance with Eq. (3.34) or the combination of the electrode reaction... 

Similarly, the ratio of dibromocarbene addition to CBr. substitution in the reaction of propyl bromide with tribromomethyl can be varied between 92 1 and 1 91, depending on whether a small and accessible quat or a bulky anion-activating quat is used (Dehmlow and... 

Polydimethyl-diallyl ammonium chloride is a strongly basic cation-active polymer. A mixture of polydimethyl-diallyl ammonium chloride and the sodium salt of carboxymethylcellulose, which is an anion-active polymer, is applied in an equimolar ratio [497] in aqueous sodium chloride solution. The proposed plugging composition has high efficiency within a wide pH range. 

Titration Procedure, ISO 2771, 1972. Synthetic Anionic Active Matter in Detergents by... 

Dealkoxycarbonylation of activated esters occurs classically under drastic thermal conditions [90]. It constitutes a typical example of a very slow-reacting system (with a late TS along the reaction coordinates) and is therefore prone to a microwave effect. The rate determining step involves a nucleophilic attack by halide anion and requires anionic activation, which can be provided by solvent-free PTC conditions under the action of microwave irradiation [91]. The above results illustrate the difficult example of cyclic /1-ketoesters with a quaternary carbon atom in the a position relative to each carbonyl group (Eq. 36). 

This type of reaction is usually best performed in DMSO solution. A simpler procedure has been proposed which uses anionic activation and microwave irradiation, with a metallic salt as the reagent and a PTC in the absence of solvent [75], This procedure was applied to the striking example of cyclic /J-ketoesters with considerable improvements (Eq. 53 and Tab. 5.25) which are readily apparent when the maximum yields obtained under classical Krapcho conditions (<20% when R-H) are considered [76],... 

This method is described in Chapt. 5 it is specific for anionic reactions because it involves anionic activation . 

Craine, J. E., Daniels, G. H. and Kaufman, S. Dopamine-beta-hydroxylase. The subunit structure and anion activation of the bovine adrenal enzyme. /. Biol. Chem. 248 7838-7844, 1973. 

Cationic 3-oxobutylidenaminatocobalt complexes (544a), with hexafluoroan-timonate as a counter anion, activate a, ft-un saturated aldehydes in 1,3-dipolar... 

It has become popular to attribute to crown ethers an anion activation effect which term suggests that their presence causes an increase in reaction rate. Although this is certainly true in many cases, it does not hold for reactions in which the ion pair is much more reactive than the free anion as a result of a cation-assisted reaction pathway. In addition to anion activation , crown ethers also exhibit cation deactivation . 

In previous sections, numerous examples of anion activation by cationic micelles and polysoaps were presented. The extent of rate augmentation— 102—lO -fold—cannot be rationalized in terms of concentration effects alone. We believe that these observations are explained most reasonably by the concept of the hydrophobic ion pair (Kunitake et al., 1976a). According to this concept, anionic reagents are activated probably due to desolvation when they form ion pairs with an ammonium moiety in a hydrophobic microenvironment. The activation of anionic species in the cationic micellar phase... 

Rabaioli G., Taglietti A. (2001) Fluorometric Detection of Anion Activity and Temperature Changes, in Valeur B. and Brochon J. C. (Eds), New Trends in Fluorescence Spectroscopy. Applications to Chemical and Life Sciences, Springer-Verlag, Berlin, pp. 209-27. 

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